/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.table.api;

import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.table.expressions.Expression;

/**
 * A table that performs flatAggregate on a {@link Table}, a {@link GroupedTable} or a {@link
 * WindowGroupedTable}.
 */
@PublicEvolving
public interface FlatAggregateTable {

    /**
     * Performs a selection operation on a FlatAggregateTable table. Similar to a SQL SELECT
     * statement. The field expressions can contain complex expressions.
     *
     * <p><b>Note</b>: You have to close the flatAggregate with a select statement. And the select
     * statement does not support aggregate functions.
     *
     * <p>Example:
     *
     * <pre>{@code
     * TableAggregateFunction tableAggFunc = new MyTableAggregateFunction();
     * tableEnv.registerFunction("tableAggFunc", tableAggFunc);
     * tab.groupBy($("key"))
     *   .flatAggregate(call("tableAggFunc", $("a"), $("b")).as("x", "y", "z"))
     *   .select($("key"), $("x"), $("y"), $("z"));
     * }</pre>
     *
     * <p>Scala Example:
     *
     * <pre>{@code
     * val tableAggFunc: TableAggregateFunction = new MyTableAggregateFunction
     * tab.groupBy($"key")
     *   .flatAggregate(tableAggFunc($"a", $"b") as ("x", "y", "z"))
     *   .select($"key", $"x", $"y", $"z")
     * }</pre>
     */
    Table select(Expression... fields);
}
